Jen -- The car art project you will be doing with your students sounds
great. If you don't mind a suggestion from a non-artist (I'm an art
historian), here it is. Just as you select a car from an impound lot to
transform into art, why not also find "sculptural materials" from
someplace similar, like a junkyard? Or you can spearhead a drive at your
school for donations of household items/materials to use in your project?
Thinking along the lines of assemblage art, your students may want to
solicit help with equipment (blowtorch, etc.) from local businesses who
deal in that stuff. Perhaps some are artistically inclined. Anyway, these
are just some thoughts. . . Good luck!